Since Nitride semiconductors have characteristics including high electron saturation velocity and a wide band gap, they may be applied to high-breakdown voltage, high-power semiconductor devices GaN, an example of a nitride semiconductor, has a wider band gap than silicon (1.1 eV) and GaAs (1.4 eV), for example, 3.4 eV; therefore, it has high breakdown field strength. Therefore, GaN may be used as a material for power devices that operate at high voltage and output high voltage for power supply applications.
The related art is disclosed in Japanese Laid-open Patent Publication Nos. 62-71301 and 5-121589 and Japanese Patent No. 3127895.